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  • 1
    Keywords: Environment ; Climate change ; Remote sensing ; Physics ; Environment ; Climate Change ; Remote Sensing/Photogrammetry ; Energy Efficiency ; Climate Change/Climate Change Impacts ; Applied and Technical Physics
    Description / Table of Contents: Part I The Urban Heat Island – Evidence, Measures and Tools --- Forecasting Models for Urban Warming in Climate Change --- Assessment Indication and Gold Standard --- Methodologies for UHI Analysis --- Decision Support Systems for Urban Planning --- Part II Pilot Actions in European Cities --- Counteracting Urban Heat Islands: Solutions for European Cities.
    Pages: Online-Ressource (LIII, 400 pages) , 213 illustrations
    ISBN: 9783319104256
    Language: English
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  • 2
    Unknown
    Berlin, Heidelberg : Springer
    Keywords: Mathematics ; Computer graphics ; Dynamics ; Ergodic theory ; Functions of complex variables ; Differential geometry ; Physics ; Mathematics ; Differential Geometry ; Functions of a Complex Variable ; Dynamical Systems and Ergodic Theory ; Computer Graphics ; Numerical and Computational Physics
    Description / Table of Contents: Discrete conformal maps: Boundary value problems, circle domains, Fuchsian and Schottky uniformization: Alexander I. Bobenko, Stefan Sechelmann, Boris Springborn --- Discrete complex analysis on planar quad-graphs: Alexander I. Bobenko and Felix Günther --- Approximation of conformal mappings using conformally equivalent triangular lattices: Ulrike Bücking --- Numerical Methods for the Discrete Map Za: Folkmar Bornemann, Alexander Its, Sheehan Olver, and Georg Wechslberger --- A variational principle for cyclic polygons with prescribed edge lengths: Hana Kourimská, Lara Skuppin, Boris Springborn --- Complex Line Bundles over Simplicial Complexes and their Applications: Felix Knöppel and Ulrich Pinkall --- Holomorphic vector fields and quadratic differentials on planar triangular meshes: Wai Yeung Lam, Ulrich Pinkall --- Vertex normals and face curvatures of triangle meshes: Xiang Sun, Caigui Jiang, Johannes Wallner, and Helmut Pottmann --- S-conical cmc surfaces. Towards a unified theory of discrete surfaces with constant mean curvature: Alexander I. Bobenko and Tim Hoffmann --- Constructing solutions to the Björling problem for isothermic surfaces by structure preserving discretization: Ulrike Bücking and Daniel Matthes --- On the Lagrangian Structure of Integrable Hierarchies: Yuri B. Suris, Mats Vermeeren --- On the variational interpretation of the discrete KP equation: Raphael Boll, Matteo Petrera, and Yuri B. Suris --- Six topics on inscribable polytopes: Arnau Padrol and Günter M. Ziegler --- DGD Gallery: Storage, sharing, and publication of digital research data: Michael Joswig, Milan Mehner, Stefan Sechelmann, Jan Techter, and Alexander I. Bobenko
    Pages: Online-Ressource (X, 439 pages) , 114 illustrations, 67 illustrations in color
    ISBN: 9783662504475
    Language: English
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  • 3
    Unknown
    Berlin, Heidelberg : Springer
    Keywords: Mathematics ; Computer graphics ; Dynamics ; Ergodic theory ; Functions of complex variables ; Differential geometry ; Physics ; Mathematics ; Differential Geometry ; Functions of a Complex Variable ; Dynamical Systems and Ergodic Theory ; Computer Graphics ; Numerical and Computational Physics
    Description / Table of Contents: Discrete conformal maps: Boundary value problems, circle domains, Fuchsian and Schottky uniformization: Alexander I. Bobenko, Stefan Sechelmann, Boris Springborn --- Discrete complex analysis on planar quad-graphs: Alexander I. Bobenko and Felix Günther --- Approximation of conformal mappings using conformally equivalent triangular lattices: Ulrike Bücking --- Numerical Methods for the Discrete Map Za: Folkmar Bornemann, Alexander Its, Sheehan Olver, and Georg Wechslberger --- A variational principle for cyclic polygons with prescribed edge lengths: Hana Kourimská, Lara Skuppin, Boris Springborn --- Complex Line Bundles over Simplicial Complexes and their Applications: Felix Knöppel and Ulrich Pinkall --- Holomorphic vector fields and quadratic differentials on planar triangular meshes: Wai Yeung Lam, Ulrich Pinkall --- Vertex normals and face curvatures of triangle meshes: Xiang Sun, Caigui Jiang, Johannes Wallner, and Helmut Pottmann --- S-conical cmc surfaces. Towards a unified theory of discrete surfaces with constant mean curvature: Alexander I. Bobenko and Tim Hoffmann --- Constructing solutions to the Björling problem for isothermic surfaces by structure preserving discretization: Ulrike Bücking and Daniel Matthes --- On the Lagrangian Structure of Integrable Hierarchies: Yuri B. Suris, Mats Vermeeren --- On the variational interpretation of the discrete KP equation: Raphael Boll, Matteo Petrera, and Yuri B. Suris --- Six topics on inscribable polytopes: Arnau Padrol and Günter M. Ziegler --- DGD Gallery: Storage, sharing, and publication of digital research data: Michael Joswig, Milan Mehner, Stefan Sechelmann, Jan Techter, and Alexander I. Bobenko
    Pages: Online-Ressource (X, 439 pages) , 114 illustrations, 67 illustrations in color
    ISBN: 9783662504475
    Language: English
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  • 4
    Keywords: Physics ; Mathematical physics ; Quantum physics ; Physics ; Quantum Physics ; Mathematical Applications in the Physical Sciences ; History and Philosophical Foundations of Physics
    Description / Table of Contents: I The Cellular Automaton Interpretation as a general doctrine: Motivation for this work --- Deterministic models in quantum notation --- Interpreting quantum mechanics --- Deterministic quantum mechanics --- Concise description of the CA Interpretation --- Quantum gravity --- Information loss --- More problems --- Alleys to be further investigated and open questions --- Conclusions --- II Calculation Techniques: Introduction to part II --- More on cogwheels --- The continuum limit of cogwheels, harmonic rotators and oscillators --- Locality --- Fermions --- PQ theory --- Models in two space-time dimensions without interactions --- Symmetries --- The discretised Hamiltonian formalism in PQ theory --- Quantum Field Theory --- The cellular automaton --- The problem of quantum locality --- Conclusions of part II --- Some remarks on gravity in 2+1 dimensions --- A summary of our views on Conformal Gravity --- Abbreviations.
    Pages: Online-Ressource (XVIII, 298 pages) , 21 illustrations, 19 illustrations in color
    ISBN: 9783319412856
    Language: English
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  • 5
    Keywords: Physics ; History ; Nuclear physics ; Heavy ions ; Hadrons ; Particle acceleration ; Physics ; Nuclear Physics, Heavy Ions, Hadrons ; History and Philosophical Foundations of Physics ; Particle Acceleration and Detection, Beam Physics ; History of Science
    Description / Table of Contents: Part I Reminiscences: Rolf Hagedorn and Relativistic Heavy Ion Research.-- Part II The Hagedorn Temperature --- Part III Melting Hadrons, Boiling Quarks Heavy Ion Path to Quark-Gluon Plasma --- Acronyms
    Pages: Online-Ressource (XVI, 441 pages)
    ISBN: 9783319175454
    Language: English
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  • 6
    Keywords: Physics ; Mathematical physics ; Quantum physics ; Physics ; Quantum Physics ; Mathematical Applications in the Physical Sciences ; History and Philosophical Foundations of Physics
    Description / Table of Contents: I The Cellular Automaton Interpretation as a general doctrine: Motivation for this work --- Deterministic models in quantum notation --- Interpreting quantum mechanics --- Deterministic quantum mechanics --- Concise description of the CA Interpretation --- Quantum gravity --- Information loss --- More problems --- Alleys to be further investigated and open questions --- Conclusions --- II Calculation Techniques: Introduction to part II --- More on cogwheels --- The continuum limit of cogwheels, harmonic rotators and oscillators --- Locality --- Fermions --- PQ theory --- Models in two space-time dimensions without interactions --- Symmetries --- The discretised Hamiltonian formalism in PQ theory --- Quantum Field Theory --- The cellular automaton --- The problem of quantum locality --- Conclusions of part II --- Some remarks on gravity in 2+1 dimensions --- A summary of our views on Conformal Gravity --- Abbreviations.
    Pages: Online-Ressource (XVIII, 298 pages) , 21 illustrations, 19 illustrations in color
    ISBN: 9783319412856
    Language: English
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  • 7
    Keywords: Physics ; History ; Nuclear physics ; Heavy ions ; Hadrons ; Particle acceleration ; Physics ; Nuclear Physics, Heavy Ions, Hadrons ; History and Philosophical Foundations of Physics ; Particle Acceleration and Detection, Beam Physics ; History of Science
    Description / Table of Contents: Part I Reminiscences: Rolf Hagedorn and Relativistic Heavy Ion Research.-- Part II The Hagedorn Temperature --- Part III Melting Hadrons, Boiling Quarks Heavy Ion Path to Quark-Gluon Plasma --- Acronyms
    Pages: Online-Ressource (XVI, 441 pages)
    ISBN: 9783319175454
    Language: English
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  • 8
    Keywords: Physics ; Quantum optics ; Physics ; Optics, Lasers, Photonics, Optical Devices ; Quantum Optics ; Popular Science in Physics ; History and Philosophical Foundations of Physics
    Description / Table of Contents: History --- A brief history of light --- Ibn Al-Haitham – Father of modern optics --- Optical Sources --- Femtosecond light --- Laser --- LED light --- Electron optics --- Applications --- Biophotonics --- Optical communication --- Optical astronomy --- Solar cells --- Optics in Remote Sensing --- Optics in nanotechnology --- Optics in art --- Eye --- Optics in medicine --- Optical illusions --- Quantum Optics --- Optical tests of foundations of physics --- Nonlinear Optics: Historical Perspectives and New Opportunities --- Quantum communication --- Nature of photon --- Atom optics --- Coherent effects: From EIT to slow light
    Pages: Online-Ressource (XX, 504 pages) , 355 illustrations, 277 illustrations in color
    ISBN: 9783319319032
    Language: English
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  • 9
    Keywords: Environment ; Climate change ; Remote sensing ; Physics ; Environment ; Climate Change ; Remote Sensing/Photogrammetry ; Energy Efficiency ; Climate Change/Climate Change Impacts ; Applied and Technical Physics
    Description / Table of Contents: Part I The Urban Heat Island – Evidence, Measures and Tools --- Forecasting Models for Urban Warming in Climate Change --- Assessment Indication and Gold Standard --- Methodologies for UHI Analysis --- Decision Support Systems for Urban Planning --- Part II Pilot Actions in European Cities --- Counteracting Urban Heat Islands: Solutions for European Cities.
    Pages: Online-Ressource (LIII, 400 pages) , 213 illustrations
    ISBN: 9783319104256
    Language: English
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  • 10
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-07-08
    Description: After many years of delays, the €1.7 billion Facility for Antiproton and Ion Research, an extension of the GSI Helmholtz Center for Heavy Ion Research near Darmstadt, Germany, may finally get built. At a council meeting on 27 and 28 June, the partner countries—eight European Union members plus India and Russia—concluded that they have enough money to cover a €320 million budget gap; they will now seek building permits from the German government. Still, some countries have yet to commit their share of the missing cash, including Russia, which had agreed to bear about 18% of FAIR's total construction cost, the second largest contribution after Germany's 70%. Author: Edwin Cartlidge
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
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  • 11
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-05-27
    Description: Author: Jelena Stajic
    Keywords: Physics
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 12
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-07-15
    Description: Author: Jelena Stajic
    Keywords: Physics
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 13
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-07-22
    Description: Author: Ian S. Osborne
    Keywords: Physics
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  • 14
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-04-08
    Description: Author: Jelena Stajic
    Keywords: Physics
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  • 15
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-25
    Description: Density functional theory (DFT) stands out from all first-principles quantum mechanical methods for the simulation of materials, as it enables very good approximations for the complicated components of electronic motion called exchange and correlation. DFT is the method of choice for many materials simulations because of the availability of general-purpose programs that can perform calculations on any material. Results obtained with one DFT program need to be reproducible by any of the other DFT programs, and this has not been straightforward up to now. On page 10.1126/science.aad3000 of this issue, Lejaeghere et al. (1) describe an extensive effort by developers of the major solid-state DFT codes to provide a unified and reproducible benchmark of precision for their calculations based on a reliable criterion, the so-called Δ gauge. Using the Δ gauge, the authors found that the level of precision that can be achieved today in DFT calculations of elemental crystalline solids is comparable to the precision of the most advanced techniques for experimental measurement of the properties of materials. The work leads to the conclusion that the DFT simulation of elemental crystalline solids is a (computationally) solved problem, but also poses the question of whether we can achieve the same levels of validation and reproducibility for more complex simulations of materials involving several elements and/or several methods. Author: Chris-Kriton Skylaris
    Keywords: Physics
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  • 16
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-07-01
    Description: The photoemission of electrons from atoms, molecules, and condensed matter provides the experimental basis of our understanding of electronic structure. During the process of photoemission, a sufficiently large quantum of electromagnetic radiation (a photon) is absorbed by matter and converted into an electronic excitation, promoting a bound electron into a final state above the vacuum energy Evac. In photoemission spectroscopy, the kinetic energy and momentum of electrons in such final states are analyzed after their propagation to a distant detector. To determine the electronic structure of the sample, the “sudden approximation” has to be fulfilled, whereby the photoelectron leaves the sample fast enough, without further interaction with the remaining electronic structure. On page 62 of this issue, Tao et al. (1) provide unprecedented insight into final-state dynamics by measuring the time a photoelectron takes to leave a solid material for characteristically different final states. By comparing an electron excited to a final state of a nickel solid Ψ Nif with one excited to a state of vacuum Ψ vacf, they establish that a photoelectron resides in the final state for 200 attoseconds (as) (2 × 10−16 s) before it leaves the nickel (see the figure). Such time scales would still allow for the electron to interact with its surroundings and, thus, are relevant for the validity of the sudden approximation. Authors: Uwe Bovensiepen, Manuel Ligges
    Keywords: Physics
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  • 17
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-06-24
    Description: Author: Jelena Stajic
    Keywords: Physics
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  • 18
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-08-16
    Description: When a multibillion-dollar physics experiment is canceled, it's tempting to look for lessons that can be applied to future megascience projects. A new book on the rise and fall of the Superconducting Supercollider (SSC) by a trio of science historians takes on that challenge. And while the authors do an excellent job of describing what occurred in the decade from its inception to its demise, they stumble when trying to assign blame. Author: Jeffrey Mervis
    Keywords: Physics
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  • 19
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-05-20
    Description: Standard superconductors consist of a condensate of paired electrons, called Cooper pairs. The transport behavior of these pairs at junctions can produce exotic effects that are of fundamental and practical interest. When two superconductors are in contact via a normal metal, the pairs must convert to single-particle states to traverse between superconductors. This occurs by the Andreev process, whereby a low-energy electron in the normal metal injects a Cooper pair into the superconductor and generates a hole that reflects back into the metal; coherent, opposite-momentum electron-hole pairs then carry the supercurrent across the metallic junction (1) (see the figure, panel A). In the case of superconductors connected to a quantum Hall state, there are only one-way paths along the junction edges. Here, a new type of Andreev process is predicted to occur, whereby electron and hole states on opposite sample edges carry the supercurrent. This prediction was made more than 20 years ago (2), but clear observation of the effect was frustrated by the difficulty of creating coexisting superconducting and quantum Hall states. On page 966 of this issue, Amet et al. (3) report on the interplay between these two states, finding evidence for the unconventional Andreev process. Their results confirm new physics that appears when two correlated states are connected, and opens the door to a range of novel excitations and exotic devices. Author: Nadya Mason
    Keywords: Physics
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  • 20
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-11
    Description: Grappling with our desire to understand nature, we construct models of the specific systems that we wish to study. Unsurprisingly, such models are generally highly tailored to the system of interest. But are all these models really that distinct? Or, could there be a universal model that can somehow describe the behavior of any system we could think of? On page 1180 of this issue, De las Cuevas and Cubitt (1) venture out to weave ideas from physics and computer science in an attempt to answer this question for all classical spin models. Author: Stephanie Wehner
    Keywords: Physics
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  • 21
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-18
    Description: The recent report of superconductivity in hydrogen sulfide (H2S) by Drozdov et al. (1) at a record high superconducting critical temperature Tc of 203 K and at high pressure (153 GPa) triggered excitement from both a fundamental and technological perspective. On page 1303 of this issue, Troyan et al. (2) confirm the finding by using an elegant and unexpected implementation of the Mössbauer technique at the third-generation synchrotron facility in Grenoble, France. They measured the Meissner effect (3)—the expulsion of magnetic field from the sample—thereby unequivocally confirming the existence of superconductivity. The new superconductor is believed to have a simple chemical formula, H3S. The superconductivity in H3S was predicted theoretically by Duan et al. (4) before the first experimental findings were reported. The technique has great potential for future studies of tiny samples squeezed to extremely high pressure. This experimental advance paves the road to probing superconductivity in metallic hydrogen, which is expected to be a room-temperature superconductor above 500 GPa (5). Author: Viktor Struzhkin
    Keywords: Physics
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  • 22
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-03-04
    Description: Turn a switch and the light goes on. The layman's perception is that this is like opening a tap so that the water starts running. But this analogy is misleading. The flow of water is governed by the theory of hydrodynamics, whereby the behavior of the fluid does not require knowledge of the motions of individual molecules. Electrical currents in solids, however, are formed from electrons. In metals, these do not collide with each other, but they do scatter from lattice imperfections. The resulting “Knudsen flow” of electrons is reminiscent of the avalanche of balls cascading through a dense forest of pins, as in a Pachinko machine. On pages 1058, 1055, and 1061 of this issue, evidence is presented that electrons can actually yield to the laws of hydrodynamics (1–3). What is additionally surprising is that these observations are in agreement with mathematical techniques borrowed from string theory (4). These techniques have been applied to describe strongly interacting forms of quantum matter, predicting that they should exhibit hydrodynamic flows (5). Author: Jan Zaanen
    Keywords: Physics
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  • 23
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-05-20
    Description: The 20th-century philosopher Wilfrid Sellars characterized the aim of philosophy as "to understand how things in the broadest possible sense of the term hang together in the broadest possible sense of the term." This is also physicist Sean Carroll's aim in his new book, The Big Picture. He sets out to show how various phenomena, including thought, choice, conscioussness, and value, hang together with the scientific account of reality that has been developed in physics in the past 100 years. He attempts to do all this without relying on specialized jargon from philosophy and physics, and succeeds spectacularly in achieving both aims. Author: Barry Loewer
    Keywords: Physics
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  • 24
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-04-22
    Description: An inherent aspect of any two-dimensional (2D) sheet is that all atoms in the material lie on the surface. This leads to a concept of 2D crystals as a “canvas,” where different chemical groups or “ink” on the surface can lead to a palette of distinct materials properties. The most well-studied 2D crystal is graphene, a one-atom-thick sheet of carbon atoms arranged in a honeycomb lattice. Although graphene's superlative materials properties and novel physical phenomena have led to a variety of applications (1), better tunability of these properties is still required. Toward this end, hydrogenated graphene (graphane) was predicted to have a wide band gap and exhibit magnetic order (2–4), in contrast to graphene, which is (semi)metallic and diamagnetic. The chemical stability of graphene makes hydrogenation difficult to control, and this has hampered efforts to tune its electronic or magnetic properties. On page 437 of this issue, González-Herrero et al. (5) report direct evidence that hydrogen atoms on graphene do indeed yield a magnetic moment and that these moments can order ferromagnetically over relatively large distances. If these methods can be extended to industrial scales, then one can imagine storing information at unprecedented densities by painting magnetic bits on graphene canvases (see the figure). Authors: S. M. Hollen, J. A. Gupta
    Keywords: Physics
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  • 25
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-04-15
    Description: Storing information in an ensemble of single-atom magnets represents the ultimate miniaturization of data storage technology, in which two specific orientations of each atomic magnetic moment represent a bit (a 0 or 1) of information (see the figure, panel A). The inherent dilemma in using a single-atom magnet is keeping it magnetized—or, in other words, being able to hold the information in one of the bit states without an external magnetic field for a useful amount of time and at practical temperatures (1, 2). This phenomenon of magnetic remanence is dif cult to realize from a single atom, in part because diminished robustness against fluctuations from the environment can unintentionally flip the magnetic state, thus wiping out the magnetic memory. A recent attempt to observe remanence in a single atom (3) proved premature, as the results were incompatible with the magnetic ground state of that system (4) and could not be reproduced (4, 5). Hence, the question of whether this defining property of a single-atom magnet can actually be achieved has remained an open question until now. On page 318 of this issue, Donati et al. (6) demonstrate that single holmium atoms exhibit magnetic remanence up to temperatures of 40 K, much higher than previous records of atomic-scale magnets composed of 3 to 12 atoms (1, 2, 5)—a record in both size and stability for any magnet. Authors: Alexander Ako Khajetoorians, Andreas J. Heinrich
    Keywords: Physics
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  • 26
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-09-30
    Description: Next week, the 2016 Nobel Prize in Physics will be announced, and many scientists expect it to honor the detection of ripples in space called gravitational waves, reported in February by scientists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO). If other prizes are a guide, the Nobel will go to the troika of physicists who 32 years ago conceived of LIGO: Rainer Weiss of the Massachusetts Institute of Technology in Cambridge, and Ronald Drever and Kip Thorne of the California Institute of Technology (Caltech) in Pasadena. But some influential physicists, including previous Nobel laureates, say the prize, which can be split three ways at most, should include somebody else: Barry Barish, a particle physicist at Caltech. Barish didn't invent LIGO, but he made it happen. The hardware at LIGO's two observatories in Hanford, Washington, and Livingston, Louisiana; the structure of the collaboration; even the big-science character of gravitational wave research—all were molded by Barish, who is now 80. Without Barish, some physicists say, there would have been no discovery. Author: Adrian Cho
    Keywords: Physics
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  • 27
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-11-04
    Description: Spectroscopy is the most accurate branch of science. Optical transition frequencies in isolated atoms and molecules can nowadays be measured to many-digit accuracies by applying the tools developed in the atomic physics community: ultrastable lasers, locked via frequency-comb lasers to atomic clocks, and the techniques to cool and control the motion of atoms. Precision measurements on small quantum systems can be compared with theoretical descriptions of these systems at the most fundamental level, allowing physics theories to be tested and enabling the search for physics beyond the standard model (1). On page 610 of this issue, Hori et al. (2) apply these tricks of the trade to a small atomic quantum system with a built-in antiparticle to perform precise spectroscopic measurement in antiprotonic helium (see the figure). The technique of buffer-gas cooling is demonstrated for the first time on a composite matter–antimatter particle. Author: Wim Ubachs
    Keywords: Physics
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  • 28
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    Nature Publishing Group (NPG)
    Publication Date: 2016-02-13
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Powell, Kendall -- England -- Nature. 2016 Feb 11;530(7589):148-51. doi: 10.1038/530148a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26863966" target="_blank"〉PubMed〈/a〉
    Keywords: Biological Science Disciplines ; Internet/utilization ; Journal Impact Factor ; Open Access Publishing ; Peer Review, Research/*trends ; *Periodicals as Topic ; Physics ; Publishing/*trends ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 29
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-08-13
    Description: Author: Jelena Stajic
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 30
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-11-04
    Description: Author: Jelena Stajic
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 31
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-10-08
    Description: Inspired by the intriguing topological phenomena recently observed in condensed-matter systems (1), a variety of different research areas, from optical to mechanical systems, have devoted their studies to topological physics. Owing to their high level of experimental controllability, cold atomic gases offer a promising platform to simulate condensed-matter models. Their charge neutrality, however, is an apparent limitation. To overcome these constraints, new experimental techniques are currently being developed that mimic the physics of charged particles. On page 83 of this issue, Wu et al. (2) report on such a new experimental technique to simulate two-dimensional (2D) spin-orbit coupling (SOC) for neutral atoms in an optical lattice—an important ingredient to explore topological quantum states. Author: Monika Aidelsburger
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 32
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-10-08
    Description: Mathematical physicist Roger Penrose stands out as an independent thinker, who for years has been critical of a few current trends in theoretical physics and cosmology. You don't have to agree with all, or even a part, of Penrose's criticism to realize that Fashion, Faith, and Fantasy in the New Physics of the Universe represents an extremely original, rich, and thoughtful survey of today's most fashionable attempts to decipher the cosmos on its smallest and largest scales, writes reviewer Mario Livio. Author: Mario Livio
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 33
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-09-30
    Description: Is time discrete or continuous? What is the smallest measurement of time that we can make? And does time actually pass faster as we age, or is it just our perception? You may consider such questions to be metaphysical or philosophical, but in Now: The Physics of Time Richard Muller ponders these and other questions through the lens of a number of major 20th century physics discoveries. In doing so, Muller successfully introduces and describes most, if not all, of the key elements in an undergraduate physics course, masterfully connecting them with the conceptual thread of "the arrow of time." Author: Lisa Jardine-Wright
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 34
    Publication Date: 2011-08-18
    Description: An interactive model for numerical computation of complicated two-dimensional flowfields including regions of reversed flow is proposed. The present approach is one of dividing the flowfield into three regions, in each of which a simplified mathematical model is applied: (1) outer, supersonic flow for which the full potential equation (hyperbolic) is used; (2) viscous, laminar layer in which the compressible boundary-layer model (parabolic) is used; and (3) recirculating flow modeled by the incompressible Navier-Stokes equations (elliptic). For matching of the numerical solutions in the three layers, two interaction models are developed: one for pressure interaction, the other for interaction between the shear layer and the recirculating flow. The uniform solution for the whole flowfield is then obtained by iteration of the local solutions under the constraints imposed by matching. The three-layer interactive model is used for solution of the flowfield past an asymmetric cavity. The method is shown to be capable of dealing with backflow without encountering problems at separation, characteristic to the boundary-layer approach.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 18; Nov. 198
    Format: text
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  • 35
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    In:  Other Sources
    Publication Date: 2011-08-17
    Description: The recently observed phenomenon of high noise radiation from the side edges of flaps in flow is investigated by way of a simple two-dimensional model problem. The model is based upon a physical picture of boundary layer vorticity being swept around the edge by spanwise flow on the flap. The model problem is developed and solved and the resulting noise radiation calculated. Further, a mathematical condition for the vortex to be captured by the potential flow and swept around the edge is derived. The results show that the sound generation depends strongly upon the strength of the vorticity and distance from the edge and that it can be more intense than the more common trailing edge noise source in agreement with the experimental observations.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 18; May 1980
    Format: text
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  • 36
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    Publication Date: 2011-08-17
    Description: The paper describes the computation of two-dimensional, subsonic, diverging internal flows and how they differ from the corresponding converging flows. Such diverging or decelerating flows occur in such obvious places as subsonic diffusers and inlets; however, such flows also occur in supersonic nozzles in the presence of a normal shock. The flow instability and its relation to the numerical method used, boundary conditions, and viscous effects are assessed both analytically and numerically. The inviscid flow is shown to be physically unstable and a poor representation of the true viscous flow.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 18; May 1980
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  • 37
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    Publication Date: 2011-08-17
    Description: Three examples of advances in computational aerodynamics; (1) three-dimensional inviscid transonic analysis, (2) design calculations for wings, and (3) the computation of viscous-induced aileron buzz, are reviewed. Attention is given to wing surface pressures, design optimization, computer memory, speed and advanced solution methods on parallel computer architecture. It is determined that many implicit approximate-factorization schemes, that have been developed for Navier-Stokes equations, can be coded to run efficiently on microprocessors.
    Keywords: AERODYNAMICS
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  • 38
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    Publication Date: 2011-08-18
    Description: A technique employed by Prandtl and Munk is adapted for the case of a wing in flapping motion to determine its lift distribution. The problem may be reduced to one of minimizing induced drag for a specified and periodically varying bending moment at the wing root. It is concluded that two wings in close tandem arrangement, moving in opposite phase, would eliminate the induced aerodynamic losses calculated
    Keywords: AERODYNAMICS
    Type: Aeronautical Journal; 84; July 198
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  • 39
    Publication Date: 2011-08-17
    Description: The turbulence downstream of a rapid contraction is calculated for the case when the turbulence scale can have the same magnitude as the mean-flow spatial scale. The approach used is based on the formulation of Goldstein (1978) for turbulence downstream of a contraction, with the added assumptions of a parallel mean flow at downstream infinity and turbulence calculated far enough downstream so that the nonuniformity of the mean flow field has decayed, and by treating the inverse contraction ratio as a small parameter. Consideration is given to the large-contraction-ratio and classical rapid-distortion theory limits, and to results at an arbitrary contraction ratio. It is shown that the amplification effect of the contraction is reduced when the spatial scale of the turbulence increases, with the upstream turbulence actually suppressed for a contraction ratio less than five and a turbulence spatial scale greater than three times the transverse dimensions of the downstream channel.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 98; June 12
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  • 40
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    Publication Date: 2011-08-17
    Description: It is noted that so far most systematic investigations on the lee side flow over delta wings at supersonic speeds are concerned with flat upper surfaces. On the basis of these results, the paper makes an attempt to characterize the different types of flow over a wing with a delta-shaped upper surface by varying a number of parameters. It is concluded that the work should be considered a first step toward systematizing the flow over delta-shaped lee sides as well.
    Keywords: AERODYNAMICS
    Type: Zeitschrift fuer Flugwissenschaften und Weltraumforschung; 4; Mar
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  • 41
    Publication Date: 2011-08-18
    Description: The thin-layer approximation is extended to an axial corner that is formed by the intersection of two perpendicular plates, one of which has an inclination angle with respect to the free stream. A computer code developed by Hung and MacCormack (1978) is modified for the thin-layer approximation, and a case with Mach 5.9 and a wedge angle of 6 deg is computed. In addition, it is shown that it is not necessary to solve the complete Navier-Stokes equations for a three-dimensional high-Reynolds-number corner flow.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 18; Dec. 198
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  • 42
    Publication Date: 2011-08-17
    Description: The effects of ablated nose shapes on the flowfield solutions are studied, using a time-dependent finite-difference method developed by Kumar, et al. (1979). Solutions are obtained for the laminar flow of a radiating mixture of H-He in chemical equilibrium past a blunt axisymmetric body at zero angle of attack. The freestream conditions correspond to a point on a typical Jovian entry trajectory, and the initial probe shape is a 45-deg half-angle spherically blunted cone. It is found that as nose bluntness increases, the following occur: in the nose region, shock standoff distances and radiative heating rates increase substantially; surface pressure level increases, but convective heating rates decrease.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 18; June 198
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  • 43
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    Publication Date: 2011-08-17
    Description: This paper presents a unified treatment of the effect of lift on peak acceleration during atmospheric entry. Earlier studies were restricted to different regimes because of approximations invoked to solve the same transcendental equation. This paper shows the connection between the earlier studies by employing a general expression for the peak acceleration and obtains solutions to the transcendental equation without invoking the earlier approximations. Results are presented and compared with earlier studies where appropriate.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets; 17; Mar
    Format: text
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  • 44
    Publication Date: 2017-10-02
    Description: Theoretical studies of aerodynamic forces on winglets shed considerable light on the mechanism by which these devices can reduce drag at constant total lift and on the necessity for proper alignment and cambering to achieve optimum favorable interference. Results of engineering studies, wind tunnel tests and performance predictions are reviewed for installations proposed for the AMST YC-14 and the KC-135 airplanes. The other major area of aerodynamic interference discussed is that of engine nacelle installations. Slipper and overwing nacelles have received much attention because of their potential for noise reduction, propulsive lift and improved ground clearance. A major challenge is the integration of such nacelles with the supercritical flow on the upper surface of a swept wing in cruise at high subsonic speeds.
    Keywords: AERODYNAMICS
    Type: AGARD Subsonic(Transonic Configuration Aerodyn.; 19 p
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  • 45
    Publication Date: 2017-10-02
    Description: Basic concepts of finite difference solution techniques for unsteady transonic flows are presented. The hierarchy of mathematical forumulations that approximate the Navier-Stokes equations are reviewed. The basic concepts involved in constructing numerical algorthms to solve these formulations are given. Semi-implicit and implicit schemes are constructed and analyzed. The discussion focuses primarily on techniques for solving the low frequency transonic small disturbance equation. This is the simplest formulation that contains the essence of inviscid unsteady transonic flow physics. The low frequency formulation is emphasized here because codes based on this theory can be run in minutes of processor time on currently available computers. Furthermore, numerical techniques involved in solving this simple formulation also apply to the more complicated formulations. Extensions to these formulations are briefly described. An indication of the present capability for solving unsteady transonic flows is provided. Important areas of future research for the advancement of computational unsteady transonic aerodynamics are described.
    Keywords: AERODYNAMICS
    Type: AGARD Spec. Course on Unsteady Aerodyn.; 24 p
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  • 46
    Publication Date: 2017-10-02
    Description: The current and projected use of advanced computers for large-scale aerodynamic flow simulation applied to engineering design and research is discussed. The design use of mature codes run on conventional, serial computers is compared with the fluid research use of new codes run on parallel and vector computers. The role of flow simulations in design is illustrated by the application of a three dimensional, inviscid, transonic code to the Sabreliner 60 wing redesign. Research computations that include a more complete description of the fluid physics by use of Reynolds averaged Navier-Stokes and large-eddy simulation formulations are also presented. Results of studies for a numerical aerodynamic simulation facility are used to project the feasibility of design applications employing these more advanced three dimensional viscous flow simulations.
    Keywords: AERODYNAMICS
    Type: AGARD The Use of Computers as a Design Tool; 12 p
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  • 47
    Publication Date: 2016-06-07
    Description: A leading edge flap design for highly swept wings, called a vortex flap, was tested on an arrow wing model in a low speed wind tunnel. A vortex flap differs from a conventional plain flap in that it has a leading edge tab which is counterdeflected from the main portion of the flap. This results in intentional separation at the flap leading edge, causing a vortex to form and lie on the flap. By trapping this vortex, the vortex flap can result in significantly improved wing flow characteristics relative to conventional flaps at moderate to high angles of attack, as demonstrated by the flow visualization results of this tests.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Supersonic Cruise Res. 1979, Pt. 1; p 131-147
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  • 48
    Publication Date: 2016-06-07
    Description: The accuracy of analytical predictions of nacelle aerodynamic interference effects at low supersonic speeds are studied by means of test versus theory comparisons. Comparisons shown include: (1) isolated wing body lift, drag, and pitching moments; (2) isolated nacelle drag and pressure distributions; (3) nacelle interference shock wave patterns and pressure distributions on the wing lower surface; (4) nacelle interference effects on wing body lift, drag, and pitching moments; and (5) total installed nacelle interference effects on lift, drag, and pitching moment. The comparisons also illustrate effects of nacelle location, nacelle spillage, angle of attack, and Mach numbers on the aerodynamic interference. The initial results seem to indicate that the methods can satisfactorily predict lift, drag, pitching moment, and pressure distributions of installed engine nacelles at low supersonic Mach numbers with mass flow ratios from 0.7 to 1.0 for configurations typical of efficient supersonic cruise airplanes.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Supersonic Cruise Res. 1979, Pt. 1; p 171-203
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  • 49
    Publication Date: 2016-06-07
    Description: Results of a low speed test conducted in the Full Scale Tunnel at NASA Langley using an advanced supersonic cruise vehicle configuration are presented. These tests used a 10 percent scale model of a configuration that had demonstrated high aerodynamic performance at Mach 2.2 during a previous test program. The low speed model has leading and trailing edge flaps designed to improve low speed lift to drag ratios at high lift and includes devices for longitudinal and lateral/directional control. The results obtained during the low speed test program have shown that full span leading edge flaps are required for maximum performance. The amount of deflection of the leading edge flap must increase with C sub L to obtain the maximum benefit. Over 80 percent of full leading edge suction was obtained up to lift off C sub L's of 0.65. A mild pitch up occurred at about 6 deg angle of attack with and without the leading edge flap deflected. The pitch up is controllable with the horizontal tail. Spoilers were found to be preferable to spoiler/deflectors at low speeds. The vertical tail maintained effectiveness up to the highest angle of attack tested but the tail on directional stability deteriorated at high angles of attack. Lateral control was adequate for landing at 72 m/sec in a 15.4 m/sec crosswind.
    Keywords: AERODYNAMICS
    Type: Supersonic Cruise Res. 1979, Pt. 1; p 35-57
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  • 50
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    Publication Date: 2019-01-25
    Description: The AD-1 airplane was designed as a low cost, low speed manned research tool to evaluate the flying qualities of the oblique wing concept. The airplane is constructed primarily of foam and fiberglass and incorporates simplicity in terms of the onboard systems. There are no hydraulics, the control system is cable and torque tube, and the electrical systems consist of engine driven generators which power the battery for engine start, cockpit gages, trim motors, and the onboard data system. The propulsion systems consist of two Microturbo TRS-18 engines sea level trust rated at 220 pounds. The airplane weighs approximately 2100 pounds and has a performance potential in the range of 200 knots and an altitude of 15,000 feet.
    Keywords: AERODYNAMICS
    Type: Society of Experimental Test Pilots Tech. Rev., Vol. 15, No. 1; p 4-5
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  • 51
    Publication Date: 2019-06-28
    Description: A method and program called TRANSEP is presented that can be used for the analysis of the flow about a low speed airfoil under high lift, massive separation conditions. Since the present program is a modification of the direct-inverse TRANDES code, it can also be used for the design and analysis of transonic airfoils, including the effects of weak viscous interaction. Interactions on program usage, program modifications to convert TRANDES to TRANSEP, and sample cases and results are given.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3376 , NAS 1.26:3376
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  • 52
    Publication Date: 2019-06-28
    Description: These basic characteristics of critical wings included wing area, aspect ratio, average thickness, and sweep as well as practical constraints on the planform and thickness near the wing root to allow for the landing gear. Within these constraints, a large matrix of wing designs was studied with spanwise variations in the types of airfoils and distribution of lift as well as some small planform changes. The criteria by which the five candidate wings were chosen for testing were the cruise and buffet characteristics in the transonic regime and the compatibility of the design with low speed (high-lift) requirements. Five wing-wide-body configurations were tested in the NASA Ames 11-foot transonic wind tunnel. Nacelles and pylons, flap support fairings, tail surfaces, and an outboard aileron were also tested on selected configurations.
    Keywords: AERODYNAMICS
    Type: NASA-CR-159332 , NAS 1.26:159332 , ACEE-06-FR-9894
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  • 53
    Publication Date: 2019-06-28
    Description: The rolling up of the trailing vortex sheet produced by a wing of finite span was calculated as a series expansion in time. For a vorticity distribution corresponding to a wing with cusped tips, the shape of the sheet was found by summing the series using Pade approximants. The sheet remains analytic for some time but ultimately develops an exponential spiral at the tips. The centroid of vorticity was conserved to high accuracy.
    Keywords: AERODYNAMICS
    Type: NASA-CR-166182 , SU-JIAA-TR-32
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  • 54
    Publication Date: 2019-06-28
    Description: Water tunnel studies were performed to define the changes that occur in vortex flow fields above the wing due to spanwise blowing over the inboard and outboard wing panels and over the trailing-edge flaps. Flow visualization photographs were obtained for angles of attack up to 30 deg and sideslip angles up to 10 deg. The sensitivity of the vortex flows to changes in flap deflection angle, nozzle position, and jet momentum coefficient was determined. Deflection of the leading edge flap delayed flow separation and the formation of the wing vortex to higher angles of attack. Spanwise blowing delayed the breakdown of the wing vortex to farther outboard and to higher angles of attack. Spanwise blowing over the trailing edge flap entrained flow downward, producing a lift increase over a wide range of angles of attack. The sweep angle of the windward wing was effectively reduced in sideslip. This decreased the stability of the wing vortex, and it burst farther inboard. Reduced wing sweep required a higher blowing rate to maintain a stable vortex. A vortex could be stabilized on the outboard wing panel when an outboard blowing nozzle was used. Blowing from both an inboard and an outboard nozzle was found to have a favorable interaction.
    Keywords: AERODYNAMICS
    Type: NASA-CR-163096 , NOR-80-138
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  • 55
    Publication Date: 2019-06-28
    Description: A theory to correct the transonic small disturbance (TSD) equation to treat strong shock waves in unsteady flow is developed. The technique involves the addition of higher order terms, which are formally of negligible magnitude, to the low frequency TSD equation. These terms are then chosen such that any shock waves in the flow have strengths approximately equal to the appropriate Rankine-Hugoniot shock strength. Two correcting approaches are investigated. The first is to derive a correction for the mean steady flow and then simply use this corrected form for oscillatory flows. The second is to derive a correction for both steady and oscillatory parts of the flow. This second development is the most satisfactory and comparisons of the present results with Euler equation results are generally favorable, particularly regarding shock location, although there are some discrepancies in the pressure distribution in the leading edge region.
    Keywords: AERODYNAMICS
    Type: NASA-CR-166157 , NEAR-TR-230
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  • 56
    Publication Date: 2019-06-28
    Description: A simplified model is used to describe the interaction between a propeller slipstream and a wing in the transonic regime. The undisturbed slipstream boundary is assumed to coincide with an infinite circular cylinder. The undisturbed slipstream velocity is rotational and is a function of the radius only. In general, the velocity perturbation caused by introducing a wing into the slipstream is also rotational. By making small disturbance assumptions, however, the perturbation velocity becomes nearly potential, and an approximation for the flow is obtained by solving a potential equation.
    Keywords: AERODYNAMICS
    Type: NASA-CR-152351
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  • 57
    Publication Date: 2019-06-28
    Description: A wind tunnel test was conducted to measure the aerodynamic characteristics of two horizontal attitude takeoff and landing V/STOL fighter/attack aircraft concepts. In one concept, a jet diffuser ejector was used for the vertical lift system; the other used a remote augmentation lift system (RALS). Wind tunnel tests to investigate the aerodynamic uncertainties and to establish a data base for these types of concepts were conducted over a Mach number range from 0.2 to 2.0. The present report covers tests, conducted in the 11 foot transonic wind tunnel, for Mach numbers from 0.4 to 1.4. Detailed effects of varying the angle of attack (up to 27 deg), angle of sideslip (-4 deg to +8 deg), Mach number, Reynolds number, and configuration buildup were investigated. In addition, the effects of wing trailing edge flap deflections, canard incidence, and vertical tail deflections were explored. Variable canard longitudinal location and different shapes of the inboard nacelle body strakes were also investigated.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81234 , A-8338
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  • 58
    Publication Date: 2019-06-28
    Description: A two dimensional cascade of harmonically oscillating airfoils was designed to model a near tip section from a rotor which was known to have experienced supersonic translational model flutter. This five bladed cascade had a solidity of 1.52 and a setting angle of 0.90 rad. Unique graphite epoxy airfoils were fabricated to achieve the realistic high reduced frequency level of 0.15. The cascade was tested over a range of static pressure ratios approximating the blade element operating conditions of the rotor along a constant speed line which penetrated the flutter boundary. The time steady and time unsteady flow field surrounding the center cascade airfoil were investigated.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165166 , EDR-10361-VOL-2
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  • 59
    Publication Date: 2019-06-28
    Description: An investigation was conducted of isolated convergent-divergent nozzles to determine the effect of several design parameters on nozzle performance. Tests were conducted using high pressure air for propulsion simulation at Mach numbers from 0.60 to 2.86 at an angle of attack of 0 deg and at nozzle pressure ratios from jet off to 46.0. Three power settings (dry, partial afterburning, and maximum afterburning), three nozzle lengths, and nozzle expansion ratios from 1.22 to 2.24 were investigated. In addition, the effects of nozzle throat radius and a cusp in the external boattail geometry were studied. The results of this study indicate that, for nozzles operating near design conditions, increasing nozzle length increases nozzle thrust-minus-drag performance. Nozzle throat radius and an external boattail cusp had negligible effects on nozzle drag or internal performance.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1766 , L-13974
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  • 60
    Publication Date: 2019-06-28
    Description: The wind tunnel tests were conducted both with and without boundary layer trips at Mach 3 and nominal free stream Reynolds numbers per meter ranging from 3.3 x 10 the 6th power. Instrumentation consisted of pressure orifices, thermocouples, a boundary layer pitot pressure rake, and a floating element skin friction balance. Measurements from both wind tunnel and flight were compared with existing engineering prediction methods.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1789 , L-14044
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  • 61
    Publication Date: 2019-06-28
    Description: Aerodynamic characteristics obtained in a helical flow environment utilizing a rotary balance located in the Langley spin tunnel are presented in plotted form. The configurations tested included the basic airplane, various control deflections, two canard locations, and wing leading edge modifications, as well as airplane components.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3170
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  • 62
    Publication Date: 2019-06-28
    Description: The application of panel methods to the calculation of vortex/surface interference characteristics in two dimensional flow was studied over a range of situations starting with the simple case of a vortex above a plane and proceeding to the case of vortex separation from a prescribed point on a thick section. Low order and high order panel methods were examined, but the main factor influencing the accuracy of the solution was the distance between control stations in relation to the height of the vortex above the surface. Improvements over the basic solutions were demonstrated using a technique based on subpanels and an applied doublet distribution.
    Keywords: AERODYNAMICS
    Type: NASA-CR-159334 , REPT-79-13
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  • 63
    Publication Date: 2019-06-28
    Description: A relatively simple equation is presented for estimating the induced drag ideal efficiency factor e for arbitrary cross sectional wing forms. This equation is based on eight basic but varied wing configurations which have exact solutions. The e function which relates the basic wings is developed statistically and is a continuous function of configuration geometry. The basic wing configurations include boxwings shaped as a rectangle, ellipse, and diamond; the V-wing; end-plate wing; 90 degree cruciform; circle dumbbell; and biplane. Example applications of the e equations are made to many wing forms such as wings with struts which form partial span rectangle dumbbell wings; bowtie, cruciform, winglet, and fan wings; and multiwings. Derivations are presented in the appendices of exact closed form solutions found of e for the V-wing and 90 degree cruciform wing and for an asymptotic solution for multiwings.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3357
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  • 64
    Publication Date: 2019-06-28
    Description: The longitudinal and lateral directional aerodynamic characteristics for two Mach 5 cruise aircraft concepts were determined for test Mach numbers of 2.96, 3.96, and 4.63. Estimates from hypersonic impact theory and first order supersonic linearized theory were compared with data to indicate the usefulness of these methods. The method which applied tangent cone empirical theory to the body and tangent wedge theory to the wings and to the horizontal and vertical tails provided the best estimates. The tangent cone empirical theory applied to all components showed poor agreement with data, and the linear theory estimates were accurate only for lift coefficient and drag coefficient at low angles of attack.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1767 , L-13868
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  • 65
    Publication Date: 2019-06-28
    Description: The trajectories of the wing tip vortices of a typical agricultural aircraft were experimentally determined by flight test. A flow visualization method, similar to the vapor screen method used in wind tunnels, was used to obtain trajectory data for a range of flight speeds, airplane configurations, and wing loadings. Detailed measurements of the spanwise surface pressure distribution were made for all test points. Further, a powered 1/8 scale model of the aircraft was designed, built, and used to obtain tip vortex trajectory data under conditions similar to that of the full-scale test. The effects of light wind on the vortices were demonstrated, and the interaction of the flap vortex and the tip vortex was clearly shown in photographs and plotted trajectory data.
    Keywords: AERODYNAMICS
    Type: NASA-CR-159382
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  • 66
    Publication Date: 2019-06-28
    Description: An implicit finite difference procedure is developed to solve the unsteady full potential equation in conservation law form. Computational efficiency is maintained by use of approximate factorization techniques. The numerical algorithm is first order in time and second order in space. A circulation model and difference equations are developed for lifting airfoils in unsteady flow; however, thin airfoil body boundary conditions have been used with stretching functions to simplify the development of the numerical algorithm.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81211 , AVRADCOM-TR-80-A-14
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  • 67
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-06-28
    Description: The potential benefits were determined for the variable camber of commercial transport airplanes designed for intercontinental and domestic missions. A variable camber concept was developed and incorporated into airplanes designed for the two missions. Benefits were evaluated by comparing the mission performance and direct operating costs for the variable camber airplanes with those for reference airplanes designed for the same missions but having fixed geometry high speed wings. Several technical uncertainties associated with implementing variable camber were also examined.
    Keywords: AERODYNAMICS
    Type: NASA-CR-158930
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  • 68
    Publication Date: 2019-06-28
    Description: A stability test program was conducted to determine the effects of airspeed, collective pitch, rotor speed and shaft angle on stability and loads at speeds beyond that attained in the BMR/BO-105 flight test program. Loads and performance data were gathered at forward speeds up to 165 knots. The effect of cyclic pitch perturbations on rotor response was investigated at simulated level flight conditions. Two configuration variations were tested for their effect on stability. One variable was the control system stiffness. An axially softer pitch link was installed in place of the standard BO-105 pitch link. The second variation was the addition of elastomeric damper strips to increase the structural damping. The BMR was stable at all conditions tested. At fixed collective pitch, shaft angle and rotor speed, damping generally increased between hover and 60 knots, remained relatively constant from 60 to 90 knots, then decreased above 90 knots. Analytical predictions are in good agreement with test data up to 90 knots, but the trend of decreasing damping above 90 knots is contrary to the theory.
    Keywords: AERODYNAMICS
    Type: NASA-CR-152373 , D210-11659-1
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  • 69
    Publication Date: 2019-06-28
    Description: The advantages of replacing the conventional wing on a transatlantic business jet with a larger, strut braced wing of aspect ratio 25 were evaluated. The lifting struts reduce both the induced drag and structural weight of the heavier, high aspect ratio wing. Compared to the conventional airplane, the strut braced wing design offers significantly higher lift to drag ratios achieved at higher lift coefficients and, consequently, a combination of lower speeds and higher altitudes. The strut braced wing airplane provides fuel savings with an attendant increase in construction costs.
    Keywords: AERODYNAMICS
    Type: NASA-CR-159361
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  • 70
    Publication Date: 2019-06-28
    Description: Two complementary methods of describing the high speed rotor noise problem are discussed. The first method uses the second order transonic potential equation to define and characterize the nature of the aerodynamic and acoustic fields and to explain the appearance of radiating shock waves. The second employs the Ffowcs Williams and Hawkings equation to successfully calculate the acoustic far field. Good agreement between theoretical and experimental waveforms is shown for transonic hover tip Mach numbers from 0.8 to 0.9.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81236 , A-8342 , AVRADCOM-TR-80-A-12
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  • 71
    Publication Date: 2019-06-28
    Description: Calibration data for the two dimensional test section of the Langley 0.3 Meter Transonic Cryogenic Tunnel were used to develop a Mach number-Reynolds number correlation for the fan pressure ratio in terms of test section conditions. Well established engineering relationships combined to form an equation which is functionally analogous to the correlation. A geometric loss coefficient which is independent of Reynolds number or Mach number was determined. Present and anticipated uses of this concept include improvement of tunnel control schemes, comparison of efficiencies for operationally similar wind tunnels, prediction of tunnel test conditions and associated energy usage, and determination of Reynolds number scaling laws for similar fluid flow systems.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1752 , L-13713
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  • 72
    Publication Date: 2019-06-28
    Description: A computational system for estimation of nonlinear aerodynamic characteristics of wings at supersonic speeds was developed and was incorporated in a computer program. This corrected linearized theory method accounts for nonlinearities in the variation of basic pressure loadings with local surface slopes, predicts the degree of attainment of theoretical leading edge thrust, and provides an estimate of detached leading edge vortex loadings that result when the theoretical thrust forces are not fully realized.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1718 , L-13589
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  • 73
    Publication Date: 2019-06-28
    Description: The inviscid and viscid effects existing within the passages of a three bladed axial flow inducer operating at a flow coefficient of 0.065 are investigated. The blade static pressure and blade limiting streamline angle distributions were determined and the three components of mean velocity, turbulence intensities, and turbulence stresses were measured at locations inside the inducer blade passage utilizing a rotating three sensor hotwire probe. Applicable equations were derived for the hotwire data reduction analysis and solved numerically to obtain the appropriate flow parameters. The three dimensional inviscid flow in the inducer was predicted by numerically solving the exact equations of motion, and the three dimensional viscid flow was predicted by incorporating the dominant viscous terms into the exact equations. The analytical results are compared with the experimental measurements and design values where appropriate. Radial velocities are found to be of the same order as axial velocities within the inducer passage, confirming the highly three dimensional characteristic of inducer flow. Total relative velocity distribution indicate a substantial velocity deficiency near the tip at mid-passage which expands significantly as the flow proceeds toward the inducer trailing edge. High turbulence intensities and turbulence stresses are concentrated within this core region. Considerable wake diffusion occurs immediately downstream of the inducer trailing edge to decay this loss core. Evidence of boundary layer interactions, blade blockage effects, radially inward flows, annulus wall effects, and backflows are all found to exist within the long, narrow passages of the inducer.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3333 , PSU-AERSP-74-2
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  • 74
    Publication Date: 2019-06-28
    Description: A numerical iterative solution to the classical Prandtl lifting-line theory, suitably modified for poststall behavior, is used to study the aerodynamic characteristics of straight rectangular finite wings with and without leading-edge droop. This study is prompted by the use of such leading-edge modifications to inhibit stall/spins in light general aviation aircraft. The results indicate that lifting-line solutions at high angle of attack can be obtained that agree with experimental data to within 20%, and much closer for many cases. Therefore, such solutions give reasonable preliminary engineering results for both drooped and undrooped wings in the poststall region. However, as predicted by von Karman, the lifting-line solutions are not unique when sectional negative lift slopes are encountered. In addition, the present numerical results always yield symmetrical lift distributions along the span, in contrast to the asymmetrical solutions observed by Schairer in the late 1930's. Finally, a series of parametric tests at low angle of attack indicate that the effect of drooped leading edges on aircraft cruise performance is minimal.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 17; Dec. 198
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  • 75
    Publication Date: 2019-06-28
    Description: Modifications were made to the model to improve longitudinal acceleration capability during transition from hovering to wing borne flight. A rearward deflection of the fuselage augmentor thrust vector is shown to be beneficial in this regard. Other agmentor modifications were tested, notably the removal of both endplates, which improved acceleration performance at the higher transition speeds. The model tests again demonstrated minimal interference of the fuselage augmentor on aerodynamic lift. A flapped canard surface also shows negligible influence on the performance of the wing and of the fuselage augmentor.
    Keywords: AERODYNAMICS
    Type: NASA-CR-152380 , DHC-DND-80-1
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  • 76
    Publication Date: 2019-06-28
    Description: The method of vortex discretization is used to analyze the interaction of the vorticity generated by a strake, with the flow over a delta wing. The validity of the approach is first established by making comparisons with established methods for dealing with delta wings, after which compound delta planforms are discussed. An understanding of the favorable interference effects normally associated with this type of configuration is obtained and results are presented to quantify the expected lift increments resulting from the strake interaction.
    Keywords: AERODYNAMICS
    Type: NASA-CR-166183 , SU-JIAA-TR-30
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  • 77
    Publication Date: 2019-06-28
    Description: Advanced performance requirements of new combat and transport aircraft together with design time constraints intensify the development and application of three dimensional computational analyses. A computational method which was developed for the specific purpose of providing an engineering analysis of complex aircraft configurations at transonic speeds. Particular attention is given to the recently incorporated wing viscous interaction and canard capabilities. The treatment of fuselage fairings, nacelles, and pylons is reviewed. The means for keeping computing resources at reasonable levels are identified. Three configurations were selected for correlations with experimental data. Taken together, the comparisons illustrate the full extent of current analysis capabilities. The configurations include: (1) a wing fuselage canard fighter; (2) a transport with fuselage fairings, four nacelles, four pylons; and (3) a space vehicle which includes an external fuel tank and rocket boosters (transonic launch configuration).
    Keywords: AERODYNAMICS
    Type: AGARD Subsonic(Transonic Configuration Aerodyn.; 13 p
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  • 78
    Publication Date: 2019-06-28
    Description: The supersonic cruise research (SCR) program, initiated in July 1972, includes system studies and the following disciplines: propulsion, stratospheric emission impact, structures and materials, aerodynamic performance, and stability and control. In a coordinated effort to provide a sound basis for any future consideration that may be given by the United States to the development of an acceptable commercial supersonic transport, integration of the technical disciplines was undertaken, analytical tools were developed, and wind tunnel, flight, and laboratory investigations were conducted. The present bibliography covers the time period from 1977 to mid-1980. It is arranged according to system studies and the above five SCR disciplines. There are 306 NASA reports and 135 articles, meeting papers, and company reports cited.
    Keywords: AERODYNAMICS
    Type: NASA-RP-1063 , L-13764
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  • 79
    Publication Date: 2019-06-28
    Description: Six interchangeable tip shapes were tested: a square (baseline) tip, an ogee tip, a subwing tip, a swept tip, a winglet tip, and a short ogee tip. In hover at the lower rotational speeds the swept, ogee, and short ogee tips had about the same torque coefficient, and the subwing and winglet tips had a larger torque coefficient than the baseline square tip blades. The ogee and swept tip blades required less torque coefficient at lower rotational speeds and roughly equivalent torque coefficient at higher rotational speeds compared with the baseline square tip blades in forward flight. The short ogee tip required higher torque coefficient at higher lift coefficients than the baseline square tip blade in the forward flight test condition.
    Keywords: AERODYNAMICS
    Type: NASA-TM-80080 , L-12774 , AVRADCOM-TR-79-49
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  • 80
    Publication Date: 2019-06-28
    Description: The time dependent Navier-Stokes equations in mass averaged variables are solved for transonic flow over axisymmetric boattail plume simulator configurations. Numerical solution of these equations is accomplished with the unsplit explict finite difference algorithm of MacCormack. A grid subcycling procedure and computer code vectorization are used to improve computational efficiency. The two layer algebraic turbulence models of Cebeci-Smith and Baldwin-Lomax are employed for investigating turbulence closure. Two relaxation models based on these baseline models are also considered. Results in the form of surface pressure distribution for three different circular arc boattails at two free stream Mach numbers are compared with experimental data. The pressures in the recirculating flow region for all separated cases are poorly predicted with the baseline turbulence models. Significant improvements in the predictions are usually obtained by using the relaxation models.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1784 , L-13826
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  • 81
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-06-27
    Description: Stall in compressors can be associated with the initiation of several types of fluid dynamic instabilities. These instabilities and the different phenomena, surge and rotating stall, which result from them, are discussed in this paper. Assessment is made of the various methods of predicting the onset of compressor and/or compression system instability, such as empirical correlations, linearized stability analyses, and numerical unsteady flow calculation procedures. Factors which affect the compressor stall point, in particular inlet flow distortion, are reviewed, and the techniques which are used to predict the loss in stall margin due to these factors are described. The influence of rotor casing treatment (grooves) on increasing compressor flow range is examined. Compressor and compression system behavior subsequent to the onset of stall is surveyed, with particular reference to the problem of engine recovery from a stalled condition. The distinction between surge and rotating stall is emphasized because of the very different consequences on recoverability. The structure of the compressor flow field during rotating stall is examined, and the prediction of compressor performance in rotating stall, including stall/unstall hysteresis, is described.
    Keywords: AERODYNAMICS
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  • 82
    Publication Date: 2019-06-27
    Description: Many modern aircraft designed for supersonic speeds employ highly swept-back and low-aspect-ratio wings with sharp or thin edges. Flow separation occurs near the leading and tip edges of such wings at moderate to high angles of attack. Attempts have been made over the years to develop analytical methods for predicting the aerodynamic characteristics of such aircraft. Before any method can really be useful, it must be tested against a standard set of data to determine its capabilities and limitations. The present work undertakes such an investigation. Three methods are considered: the free-vortex-sheet method (Weber et al., 1975), the vortex-lattice method with suction analogy (Lamar and Gloss, 1975), and the quasi-vortex lattice method of Mehrotra (1977). Both flat and cambered wings of different configurations, for which experimental data are available, are studied and comparisons made.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 17; Jan. 198
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  • 83
    Publication Date: 2019-06-27
    Description: A finite difference code for predicting the high speed flow over the advancing helicopter rotor is presented. The code solves the low frequency, transonic small disturbance equation and is suitable for modeling the effects of advancing blade unsteadiness on blades of nearly arbitrary planform. The method employs a quasi-conservative mixed differencing scheme and solves the resulting difference equations by an alternating direction scheme. Computed results showed good agreement with experimental blade pressure data and illustrate some of the effects of varying the rotor planform. The flow unsteadiness is shown to be an indispensible part of a transonic solution. Close to the tip at high advance ratio, cross flow effects can significantly affect the solution.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1721 , A-8024
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  • 84
    Publication Date: 2019-06-27
    Description: Calculated and measured values of helicopter rotor flapping angles in forward flight are compared for a model rotor in a wind tunnel and an autogiro in gliding flight. The lateral flapping angles can be accurately predicted when a calculation of the nonuniform wake-induced velocity is used. At low advance ratios, it is also necessary to use a free wake geometry calculation. For the cases considered, the tip vortices in the rotor wake remain very close to the tip-path plane, so the calculated values of the flapping motion are sensitive to the fine details of the wake structure, specifically the viscous core radius of the tip vortices.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81213 , AVRADCOM-TR-80-A-11 , A-8239
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  • 85
    Publication Date: 2019-06-27
    Description: The effectiveness of leading edge concepts for minimizing or controlling leading edge flow separation was studied. Emphasis was placed on low speed performance, stability, and control characteristics of configurations with highly swept wings. Simple deflection of the leading edge, a variable camber leading edge system, and a leading edge vortex flow system were among the concepts studied. The data are presented without analysis.
    Keywords: AERODYNAMICS
    Type: NASA-TM-80180
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  • 86
    Publication Date: 2019-06-27
    Description: A computer implemented numerical method for predicting the flow in and about an isolated three dimensional jet exhaust nozzle is summarized. The approach is based on an implicit numerical method to solve the unsteady Navier-Stokes equations in a boundary conforming curvilinear coordinate system. Recent improvements to the original numerical algorithm are summarized. Equations are given for evaluating nozzle thrust and discharge coefficient in terms of computed flowfield data. The final formulation of models that are used to simulate flow turbulence effect is presented. Results are presented from numerical experiments to explore the effect of various quantities on the rate of convergence to steady state and on the final flowfield solution. Detailed flowfield predictions for several two and three dimensional nozzle configurations are presented and compared with wind tunnel experimental data.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3264 , LMSC-D678888-PT-2
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  • 87
    Publication Date: 2019-06-27
    Description: Water tunnel studies were performed to qualitatively define the flow field of the F-14. Particular emphasis was placed on defining the vortex flows generated at high angles of attack. The flow visualization tests were conducted in the Northrop water tunnel using a 1/72 scale model of the F-14 with a wing leading-edge sweep of 20 deg. Flow visualization photographs were obtained for angles of attack up to 55 deg and sideslip angles up to 10 deg. The F-14 model was investigated to determine the vortex flow field development, vortex path, and vortex breakdown characteristics as a function of angle of attack and sideslip. Vortex flows were found to develop on the highly swept glove and on the upper surface of the forebody. At 10 deg of sideslip, the windward glove vortex shifted inboard and broke down farther forward than the leeward glove vortex. This asymmetric breakdown of the vortices in sideslip contributes to a reduction in the lateral stability above 20 deg angle of attack. The initial loss of directional stability is a consequence of the adverse sidewash from the windward vortex and the reduced dynamic pressure at the vertical tails.
    Keywords: AERODYNAMICS
    Type: NASA-CR-163098 , NOR-80-150 , H-1135
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  • 88
    Publication Date: 2019-06-27
    Description: Automatic flare and decrab control laws for conventional takeoff and landing aircraft were adapted to the unique requirements of the powered lift short takeoff and landing airplane. Three longitudinal autoland control laws were developed. Direct lift and direct drag control were used in the longitudinal axis. A fast time simulation was used for the control law synthesis, with emphasis on stochastic performance prediction and evaluation. Good correlation with flight test results was obtained.
    Keywords: AERODYNAMICS
    Type: NASA-CR-152365
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  • 89
    Publication Date: 2019-06-27
    Description: Aerodynamic characteristics obtained in a helical flow environment utilizing a rotary balance located in the Langley spin g tunnel are presented in plotted form for a 1/6 scale, single engine, high wing, general aviation model. The configurations tested included the basic airplane and control deflections, wing leading edge devices, tail designs, and airplane components. Data are presented without analysis for an angle of attack range of 8 deg to 90 deg and clockwise and counter clockwise rotations covering a spin coefficient range from 0 to 0.9.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3201
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  • 90
    Publication Date: 2019-06-27
    Description: An approximate method for computing the jet noise pattern of a maneuvering airplane is described. The method permits one to relate the noise pattern individually to the influences of airplane speed and acceleration, jet velocity and acceleration, and the flight path curvature. The analytic formulation determines the ground pattern directly without interpolation and runs rapidly on a minicomputer. Calculated examples including a climbing turn and a simple climb pattern with a gradual throttling back are presented.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1733 , L-13629
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  • 91
    Publication Date: 2019-06-27
    Description: Theodorsen's circulation function relates lift to downwash in unsteady two dimensional incompressible flow. A continued fraction representation for the circulation function is described. The continued fraction converges and has a particularly simple coefficient pattern.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81838
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  • 92
    Publication Date: 2019-06-27
    Description: In order to provide experimental data for comparison with newly developed finite difference methods for computing supersonic flows over aircraft configurations, wind tunnel tests were conducted on four arrow wing models. The models were machined under numeric control to precisely duplicate analytically defined shapes. They were heavily instrumented with pressure orifices at several cross sections ahead of and in the region where there is a gap between the body and the wing trailing edge. The test Mach numbers were 2.36, 2.96, and 4.63. Tabulated pressure data for the complete test series are presented along with selected oil flow photographs. Comparisons of some preliminary numerical results at zero angle of attack show good to excellent agreement with the experimental pressure distributions.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81835 , L-13703
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  • 93
    Publication Date: 2019-06-27
    Description: An investigation was conducted in the Langely 6 by 28 inch transonic tunnel to determine the two dimensional aerodynamic characteristics of three helicopter rotor airfoils at Reynolds numbers from typical model scale to full scale at Mach numbers from about 0.35 to 0.90. The model scale Reynolds numbers ranged from about 700,00 to 1,500,000 and the full scale Reynolds numbers ranged from about 3,000,000 to 6,600,000. The airfoils tested were the NACA 0012 (0 deg Tab), the SC 1095 R8, and the SC 1095. Both the SC 1095 and the SC 1095 R8 airfoils had trailing edge tabs. The results of this investigation indicate that Reynolds number effects can be significant on the maximum normal force coefficient and all drag related parameters; namely, drag at zero normal force, maximum normal force drag ratio, and drag divergence Mach number. The increments in these parameters at a given Mach number owing to the model scale to full scale Reynolds number change are different for each of the airfoils.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1701 , L-13139 , AVRADCOM-TR-80-B-5
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  • 94
    Publication Date: 2019-06-27
    Description: The time-domain equations of motion of elastic airfoil sections forced by control surface motions and gusts were developed for the case of incompressible flow. Extensive use was made of special functions related to the inverse transform of Theodorsen's function. Approximations for the special cases of zero stream velocity, small time, large and time are given. A numerical solution technique for the solution of the general case is given. Examples of the exact transient response of an airfoil are presented.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81351 , H-1125 , REPT-505-36-24
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  • 95
    Publication Date: 2019-06-27
    Description: Digitally acquired and processed results from an experimental investigation of grid generated turbulence of various scales through and downstream of nine matched cubic contour contractions ranging in area ratio from 2 to 36, and in length to inlet diameter ratio from 0.25 to 1.50 are reported. An additional contraction with a fifth order contour was also utilized for studying the shape effect. Thirteen homogeneous and nearly isotropic test flow conditions with a range of turbulence intensities, length scales and Reynolds numbers were generated and used to examine the sensitivity of the contractions to upstream turbulence. The extent to which the turbulence is altered by the contraction depends on the incoming turbulence scales, the total strain experienced by the fluid, as well as the contraction ratio and the strain rate. Varying the turbulence integral scale influences the transverse turbulence components more than the streamwise component. In general, the larger the turbulence scale, the lesser the reduction in the turbulence intensity of the transverse components. Best agreement with rapid distortion theory was obtained for large scale turbulence, where viscous decay over the contraction length was negligible, or when a first order correction for viscous decay was applied to the results.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165136 , R80-1
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  • 96
    Publication Date: 2019-06-27
    Description: The question of the effect of distribution and magnitude of spanwise circulation and shed vorticity from an airplane wing on the distribution pattern of agricultural products distributed from an airplane was studied. The first step in an analysis of this question is the determination of the actual distribution of lift along an airplane wing, from which the pattern of shed vorticity can be determined. A procedure is developed to calculate the span loading for flapped and unflapped wings of arbitrary aspect ratio and taper ratio. The procedure was programmed on a small programmable calculator, the Hewlett Packard HP-97, and also was programmed in BASIC language. They could be used to explore the variations in span loading that can be secured by variable flap deflections or the effect of flying at varying air speeds at different airplane gross weights. Either an absolute evaluation of span loading can be secured or comparative span loading can be evaluated to determine their effect on swath width and swath distribution pattern. The programs are intended to assist the user in evaluating the effect of a given spanload distribution.
    Keywords: AERODYNAMICS
    Type: NASA-CR-159329
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  • 97
    Publication Date: 2019-06-27
    Description: An analytical technique for the prediction of fan blade flutter was evaluated by utilizing first stage fan flutter data from tests on an advanced high performance engine. The formulation includes both aerodynamic and mechanical coupling among all the blades of the assembly. Mistuning is accounted for in the analysis so that individual blade inertias, frequencies, or damping can be considered. Airfoil stability was predicted by calculating a flutter determinant, the eigenvalues of which indicate the extent of susceptibility to flutter. When blade to blade differences in frequencies are considered, a stable system is predicted for the test points examined. For a tuned system, it was found that torsional flutter can be predicted at a limited number of interblade phase angles. Examination of these phase angles indicated that they were "close" to the condition of acoustic resonance. For the range of Mach numbers and reduced frequencies considered, the so called subcritical flutter cannot be predicted. The essential influence of mechanical coupling among the blades is to change the frequencies of the system with little or no change in damping; however, aerodynamic coupling together with mechanical coupling could change not only frequencies, but also damping in the system, with a trend toward instability.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165137 , R80-914545-16
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  • 98
    Publication Date: 2019-06-27
    Description: Static and forward speed tests were made in a 40 multiplied by 80 foot wind tunnel of a large-scale, ejector-powered V/STOL aircraft model. Modifications were made to the model following earlier tests primarily to improve longitudinal acceleration capability during transition from hovering to wingborne flight. A rearward deflection of the fuselage augmentor thrust vector was shown to be beneficial in this regard. Other augmentor modifications were tested, notably the removal of both endplates, which improved acceleration performance at the higher transition speeds. The model tests again demonstrated minimal interference of the fuselage augmentor on aerodynamic lift. A flapped canard surface also showed negligible influence on the performance of the wing and of the fuselage augmentor.
    Keywords: AERODYNAMICS
    Type: NASA-CR-163578 , DHC-DND-80-1
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  • 99
    Publication Date: 2019-06-27
    Description: The potential advantages of bank-to-turn control are summarized. Recent and current programs actively investigating bank-to-turn steering are reviewed and critical technology areas concerned with bank-to-turn control are assessed.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3325
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  • 100
    Publication Date: 2019-06-27
    Description: Pressure distributions on a wing body at Mach 4.63 are calculated. The combined theory is shown to give improved predictions over either linear theory or impact theory alone. The combined theory is also applied in the inverse design mode to calculate optimum camber slopes at Mach 4.63. Comparisons with optimum camber slopes obtained from unmodified linear theory show large differences. Analysis of the results indicate that the combined theory correctly predicts the effect of thickness on the loading distributions at high Mach numbers, and that finite thickness wings optimized at high Mach numbers using unmodified linear theory will not achieve the minimum drag characteristics for which they are designed.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3314
    Format: application/pdf
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